State officials say an 81-year-old man in Lenawee County is this year's first human case of West Nile virus in Michigan.

The Michigan Department of Community Health said Monday the man started showing symptoms of the disease in late July and has been in the hospital since early this month.

The agency also says Michigan State University's Diagnostic Center for Population and Animal Health detected West Nile virus in a crow found dead in Lenawee County on July 23.

Mosquitoes transmit the virus. Most people bitten by an infected mosquito show no symptoms but some become sick within a few days.

About one in five infected persons will become mildly ill. Severe cases may result in encephalitis, meningitis or death.